Eye tracking technology determines the gaze point and length of gaze of a user. It can indicate to a computer where on, and for how long thereupon, a user is looking at a computer monitor, thus replacing the traditional PC mouse. Selections can be made by a slow blink or other switching mechanisms. Together with companion software, such as on-screen keyboards and voice recognition software, an eye tracker system becomes a completely hands-free method for computer use.
A number of eye tracking devices are available that track the eye movement and other elementary eye behaviors. Typical systems operate by mounting an eye tracking device adjacent to the computer monitor. The eye monitoring device is generally equipped with an infrared light-emitting diode, or LED. The LED bounces light off of the user's cornea and retina and the eye monitoring device records the reflections and sends the signals to software, which move the cursor to the spot where the user is looking. With these types of eye tracking systems, the cursor is positioned on a video screen according to the calculated gaze of the user. A number of different techniques have been developed to select a target in these systems.
For example, Chang et al. disclose in U.S. patent application Ser. No. 2002/0010707 A1, a system in which a user focuses on an annotation tag which can be determined by tracking the position of a conventional screen displayed pointer maneuverable by mouse, stylus, or keyboard, by use of touch sensitive overlays to a screen, eye or head tracking system, or any other conventional mechanism for reliably determining a user focus on a region of a screen display. Initiating dynamic display of supporting information at the user focus can be in response to user initiated mouse clicks, keyboard input, finger taps, duration (e.g. mouse cursor held still on or adjacent to an annotation tag for one tenth of a second to about two seconds, with one second being typical), or any other suitable input scheme for confirming a user desire to view supporting bodies of data. Accommodation of the supporting body of data can be through overlay or spatial morphing of the primary body of data. An overlay presentation replaces the annotation tag with supporting data, while concurrently identifying the annotated region of the primary body by suitable callouts, lines, markers, or animations that place the annotation in the margin, interline, or inter paragraph region, but still direct a user's attention to the related region of the primary body.
Tognazzini et al. disclose in U.S. Pat. No. 5,831,594, a method and apparatus for eye track derived backtrack to assist a computer user to find a last gaze position prior to an interruption of eye contact. The system of Tognazzini et al. indicates lost context by scrolling a virtual page and highlighting the last entity of a virtual page that had the last fixation immediately prior to the interruption. The lost context is marked in a number of ways to assist the user in reacquiring the context.
Other conventional methods of assisting a user to recall screen context include mouse trails and trackpoint accessibility features. A mouse trail is a feature of a Graphical User Interface (GUI) which causes the mouse pointer to leave a trail of mouse arrows that fade away as a user moves the mouse across the screen. Mouse trails are for normal user controlled mouse movements, and are a history of indicators of the source of the mouse pointer. They typically appear on the screen for a few milliseconds. Mouse trails keep track of approximately eight recent pointer positions, only erasing the oldest. At any time, there may be up to, for example, eight sequential pointers on the screen, but if the mouse is still, they will all be in the same position, and so only one will be visible. When the mouse moves, it appears to leave a trail of pointers behind it, and this can increase the visibility of the pointer.
A TrackPoint™ (TrackPoint is a registered trademark of International Business Machines Corporation.) Accessibility feature is a pulsing animation around the mouse pointer that is activated by the Control (Cntrl) key in Windows® XP (Windows is a registered trademark of Microsoft Corporation). It lets users find the mouse pointer more easily by providing a visual cue via a brief animation to enable a user to quickly locate the pointer on the display screen. This option is helpful for people with visual impairments.
Other conventional solutions to maintain visual feedback for a user of an eye tracking system include recording the screen location of where a user is looking and then jumping or “warping” the mouse pointer ahead to that location. A “pointer warp” can be described as occurring when the mouse pointer “jumps” to another part of the screen. A pointer warp is not a smooth transition, instead it skips ahead. A problem with the use of the pointer warp is that it can be disconcerting as well as disconnected. The mouse pointer jumps to the user's focus of attention, but there is no continuity with where it was previously. Another problem that exists during use of the conventional pointer warp involves the reading of text as a user can lose track of the line that is being currently read or when switching to a new line. As lines get longer, the problem grows.